Use of the monoclonal antibody benralizumab was associated with lower eosinophil counts than placebo in patients with platelet-derived growth factor receptor alpha (PDGFRA)-negative hypereosinophilic syndrome, according to results from a double-blind, placebo-controlled, phase 2 trial published in the New England Journal of Medicine.

“People living with a rare disease often have few, if any, effective treatment options,” Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), stated in a press release. “This promising treatment advance for people with hypereosinophilic syndromes is just one example of how NIH research responds to the unique medical needs of individuals with rare diseases.”

Syringe and vials. Source: Getty

Patients in the trial had a diagnosis of PDGFRA-negative hypereosinophilic syndrome (HES) with an absolute eosinophil count of ≥ 1,000 cells per cubic millimeter received 30 mg of benralizumab or placebo (n = 20) for 12 weeks or placebo. Prior to the trial, patients were stable on HES therapy for a minimum of 1 month before beginning treatment. The 12-week randomized treatment phase was followed by an unblinded 12-week open-label phase and 24-week open-label extension phase where absolute eosinophil counts were known and patients could taper their background therapy.

In the first phase, 90% of patients who randomly received benralizumab had a minimum of 50% absolute eosinophil count at 12 weeks compared with 30% of patients in the placebo group (P = .02). In the open-label portion of the trial, 17 of 19 patients (89%) had clinical and hematologic responses to the treatment, and 14 of 19 patients (74%) maintained these responses until 48 weeks. Among patients who were still receiving benralizumab at week 48, 9 of 14 patients (64%) were able to taper their background therapies.

With regard to adverse events, 32% patients reported elevated lactate dehydrogenase combined with headache after the initial dose, but all patients said these side effects resolved within 48 hours, and there were similar overall adverse event rates between groups.

“[T]he trial showed that benralizumab therapy is effective in reducing blood and tissue eosinophilia with few or no toxic effects in patients with severe, treatment-refractory hypereosinophilic syndrome, despite having markedly higher eosinophil levels than patients with asthma,” Dr. Fauci and colleagues concluded. “Equally important for this chronic and debilitating disorder, the eosinophillowering effect of benralizumab was sustained in the majority of patients despite tapering of other therapies that have substantial long-term toxic effects.”